Opto-electric color correction apparatus



Oct. 19, 1954 P. N. CURRY OPTOELECTRIC COLOR CORRECTION APPARATUS 2Sheets-Sheet 1 Filed Feb. 9. 1951 PAUL N. CURRY w olkiomzu IN VEN TOR.

ATTOPNE'Y Oct. 19, 1954 P. N. CURRY OPTOELECTRIC COLOR CORRECTIONAPPARATUS 2 Sheets-Sheet 2 Filed Feb. 9, 1951 PAUL N. CURRY INVENTO ATTOPNEY Patented Oct. 19, 1954 OPTO-ELECTRIC COLOR CORRECTION APPARATUSPaul N. Curry, Kalamazoo, Mich.

Application February 9, 1951, Serial No. 210,265

13 Claims.

This invention relates to color photography and particularly to the partthereof involved in the making of the color separation negatives fromcolor transparencies.

There are many processes of making color prints, either uponphotographic paper or in the photoengraving art, but the most usable ofcommercially applicable processes involves the preparation of eitherthree or four negatives, according to the process used,'which negativesare made so that they represent each of the following colorcharacteristics in the transparency; red, green, blue and black, Black,however, is sometimes omitted. From each of these negatives, there maybe made a photographic print, or there may be made a photoengravingplate depending upon the ultimate purpose to be served.

However, because of the discrepancies in color responding capacitybetween the articles appearing in nature which are photographed, thedyes used in the transparencies, the dyes used in photographic printingand the inks used in book or magazine printing of color pictures, theremust always be a considerable amount of toning of each separationnegative to accommodate it to the above discrepancies, in order that thefinal result shall present a picture to which the eye will react inabout the same way that it would to the original scene in nature.

This toning is done, in presently practiced methods, by a complex systemof masking. This comprises printing along with the negative representingone selected color, a weak positive bound into register with saidnegative and which positive represents the complementary color of thesaid negative in order to obtain a corrected positive print of the saidselected color. By this manipulation, or others similar, the printingstrength of a particular color in the positive print may be built up ortoned down as desired to correct for the above mentioned discrepancies.

However, this correction my masking involves many difficulties, amongthe most prominent of which is the inherent mechanical difiiculty ofprinting through two transparencies at the same time and the fact thatthe masks can never be made by definite analysis but must be madeaccording to the best judgment of the operator. Further, this processfrequently requires that many trial maskings be made before a whollysatisfactory one can be obtained and, hence, is extremely wasteful.

Further, it has been found desirable in recent years to effect colorcorrection by the use of a masking procedure utilizing a weak negativerather than a weakpositive. Inasmuch as particular operators may preferone method or the other method, and on occasion it has been found thatsometimes one method is preferable in a given instance and at othertimes the other method will be preferable, it is desirable to produceapparatus carrying out such color correcting procedures which apparatusmay be able by relatively simple adjustment to carry out either of thesemethods.

Also, although the black printer is often omitted in the making of colorprinting plates, it is universally recognized that a much better picturewill result of one is used. The difficulty, however, in the making ofblack printing plates arises from the difficulties in analyzingdensities in a manner to reproduce accurately on the plate being exposedthe true densities of the transparencies to be reproduced. Previousattempts to meet this problem by combining exposures from colorseparations has been unsatisfactory because these will v give black inareas where there is a single pure color in the transparencies. This isnot desirable for true color rendition in the printing industry but itis desirable to make a black printing plate which will show black orgray in the areas of the transparencies where it is really black orgray. If such an operation can be carried out by the same machine thatwill accomplish the solution of the above outlined problems, and thusmake necessary employment of only a single piece of apparatus to meetall of the various above described problems, it will be readily seenthat such an apparatus would be of extremely high utility.

In my Patent No. 2,309,048 I disclosed the basic outlines of a methodand apparatus which would meet both or all of the above describedproblems. However, the specific apparatus therein disclosed had certainoperating difficulties, principally the difiiculty of securing sharpdifferentiation of the respective light beams, which has restricted itscommercial attractiveness. Therefore, I have developed an improvedapparatus for practicing said method by which a truly sharpdifferentiation may be secured, one which is considerably less expensiveto build and one which has a somewhat wider range of controls. It is mypresent purpose to disclose and claim such apparatus herein.

Thus, a principal object of my invention is to provide an improvedapparatus for carrying out the general method disclosed in my above mentioned Patent No. 2,309,048.

A further object of the invention is to provide apparatus carrying outsaid method which is relatively simple to construct.

A further object of the invention is to provide apparatus, as aforesaid,which will be reliable and accurate in operation.

A further object of the invention is to provide an apparatus, asaforesaid, which will have a wide range of adjustability, and therebyenable it to carry out a wide range of specific operations.

A further object of the invention is to provide apparatus, as aforesaid,which will effect correction of color intensities accurately andefficiently.

A further object of the invention is to provide apparatus, as aforesaid,which will effect desired color intensity corrections in the exposure ofa photographic negative and which will do so in stantaneously andautomatically but subject to the control of an operator.

A further object of this invention is to provide apparatus, asaforesaid, for preparing from a colored transparency a black printingplate or positive printer which will automatically eliminate all blackfrom regions in the plate which are occupied by a single pure color asdistinguished from mixtures of color or from black and which willproperly correct gray areas in other parts of said transparency.

Other objects and purposes of my invention will be obvious to personsacquainted with apparatus of this general nature upon reading thefollowing disclosure and examination of the accompanying drawings.

In the drawings:

Figure 1 shows a schematic diagram of apparatus built in accordance withthis invention and adapted to handle one color at a time.

Figure 2 illustrates a modification adapted to handle a plurality ofcolors as used in moving picture film.

Figure 3 is a fragmentary view generally similar to the transparencyexposing apparatus shown in Figure 1 and showing a modification thereof.

General description The apparatus of this invention provides a pilotbeam, within the meaning of the above mentioned Patent No. 2,309,048,usually comprising polychromatic light including the three primarycolors, of intermittent character and of precisely controlled frequencyof intermittency. There is provided, simultaneously, another beam oflight, comprising one of the three primary colors and this beamconstitutes an exposing beam of com stant emanation. These two beams areblended into a single beam and directed onto a scanning device whichdirects them onto elemental areas of the transparency examined. Aportion of the light passing through the transparency is split off fromthe main beam and onto a succesion of dispersion devices by which it isdivided into red, green and blue components and these are directed ontosuitable light sensitive devices. The remainder of the light passing thetransparency is directed onto the light sensitive material beingexposed, with or without separation into its monochromatic constituentsaccording to the end product desired.

Said light sensitive devices are connected into filter circuits, theoutput of which is limited to the frequency of the pilot beam. Theoutput potentials of the three filter circuits are then separatelymodulated as desired and imposed as controlling potentials onto a lightvalve placed in the exposing beam. Thus, the exposing beam may beincreased or decreased in intensity in accordance with the analysis ofthe transparency made by the pilot beam. Such analysis beingsubstantially instantaneous and therefore instantaneous for allpractical purposes, said exposing beams are directed onto the lightsensitive materials in their corrected intensity.

Reference is herein generally made for illustrative purposes to thecopying of transparencies, but it Will be appreciated that theprinciples hereof are equally adaptable to copying opaque pictures.Hence, language referring to transparencies should be taken asillustrative and not limiting.

Detailed explanation Referring to Figure l of the drawings, there isshown schematically one specific embodiment of a device illustrating theprinciples of the present invention.

There are provided two light sources, I and 2, respectively. Lightsources I and 2 are of such a nature as will produce polychromatic lightcontaining selected ones of three primary colors, and preferably whichwill produce a substantially pure white beam.

Placed in the path of each of these beams are devices for altering saidbeams to give them selected characteristics. In the path of the beam 6there is interposed a light valve ll of any conventional kind by whichthe beam may be broken into a plurality of small segments ofpredetermined length. One advantageous type of such light valve is thewell known Kerr cell operated by a high frequency oscillator l2 whichmay be precisely tuned to a selected frequency. Interposed in the beam 1is a light valve ll which is of any conventional character, as a Kerrcell, capable of passing greater or lesser quantities of light ininfinite increments as determined by an applied electrical potential.

These beams'of light are arranged to fall upon a prism 24 by which saidbeams are gathered and directed through a suitable lens group 26 bywhich a beam 21 of substantially parallel rays is provided. Said beam 21is directed onto the scanning device 28. Said scanning device may be ofany conventional character or it may be that disclosed in my applicationNo. 2,309,048. From said scanning device, the beam 29a is directed ontothe transparency 30 and caused to scan same in whatever particularpattern is desirable, such as that described in my Patent No. 2,309,048.Said beam 29 passes through the transparency 30 and falls next upon amirror 3|. One portion of said mirror has a small opening 32 therein.Said mirror reflects a portion of said beam, as beam 33, to and througha lens system 34 onto the transparent mirrors 36 and 31.

The portion of said beam 29 which passes through the opening 32 passesthrough the filter to be rendered as nearly monochromatic as possibleand is then gathered by the lens 38 and directed onto the photosensitive plate 43.

The beam of light 33 striking the transparent mirrors 36 and 31 isbroken into the beams 40, 4! and 42 which are caused, respectively, topass through the red, blue and green filters '64, 65 and 10 and thenstrike the light sensitive devices 47, 43 and 49 of the interpretingsection 50. Such light sensitive devices may be of any conventional kindbut are conveniently photo-electric tubes of any standard make. Each ofsaid photo-electric tubes is connected through a frequency filteringcircuit to the respective output conductors 59, BI and 62. Saidfiltering circuits may be of any conventional kind but may convenientlybe as illustrated in the drawings. These comprise a capacitor which isconnected in parallel with a primary winding 56 and said parallelcircuit is connected respectively to the principal electrodes of thephototube 49. The secondary winding 51 is associated with said primarywinding 56 in inductive rela tion therewith and is connected in parallelwith 'a capacitor 59. The ends of said last named parallel circuit areconnected respectively to ground and to the filter output conductor 62.The other light sensitive devices 41 and 48 are similarly connected tothe respective filter output conductors 59 and iii.

The red sensitive output conductor 59 connects first to an amplifier 69of a conventional sort which may hereinafter be referred to as a redamplifier and it is in turn connected to devices of a conventional sortby which the impulses from said red amplifier may be mixed in selectableproportions with impulses from other amplifiers hereinafter mentionedand produce a single integrated output. These elements are collectivelysometimes hereinafter designated as the color modulating section 60.Said red amplifier is connected to a red-blue mixer 'II and to ablue-red mixer I2. Said red-blue mixer "II is connected to red-greenmixer I3 and the output of said red-green mixer is connected to aterminal I4 of the switch T6. The armature I5 of the selector switch I6is connected to the light valve I! for energizing same to control theamount of light passing from the source I to the gathering prism 24.

The blue output conductor 6I is connected first to a blue amplifier 78of a conventional type and preferably of the same type as the redamplifier 69. Said blue amplifier is connected to the bluered mixer I2,to the red-blue mixer H and to a green-blue mixer 19. The blue-red mixer12 is then connected to a blue-green mixer 9| and this is connected tothe terminal 82 of the selector switch I6.

The green output conductor 62 is connected to a green amplifier 83 of aconventional type and preferably similar to the red and blue amplifiers69 and 78. The said green amplifier is connected to the green-blue mixerI9 and to the red-green mixer I3. The green-blue mixer 19 is connectedto a green-red mixer 84 and this in turn is connected to the terminal 66of the selector switch 16. Each of said mixers are of conventional sortsand function to mix the respective input pulses in predeterminableproportions and produce single integrated output pulse comprising asummation of each of the input pulses.

Now turning to the portion of the device utilized in making a blackprinting negative there is shown broadly a gray modulating part 9! and acomparator-selector portion 92. Each is supplied through appropriatecircuitry from the color output conductors 59, 6! and 62 and each hascircuitry enabling it to effect desired control over the light valve I'Iupon proper position of the selector switch I6.

More specifically, the conductors 95, 93 and 94 are respectivelyenergized from the conductors 59, 6i and 62. Pulses from the conductor95 are led first to a green amplifier 96 of conventional sort andpreferably of nature similar to the green amplifier 83. The output ofsaid green amplifier 99 is supplied to the green-blue mixer 91 and theoutput thereof is supplied to the greenred mixer 98. The output of saidlast named green-red mixer is supplied to the terminal 99 of theselector switch IN. The conductor 93 I 02, a blue-red mixer I03 and ablue-green mixer 651 I04 to the terminal I06 of the selector switch IN.The conductor 94 is likewisesimilarly connected through the redamplifier I01, the redgreen mixer I08 and the red-blue mixer I09 to theterminal III of the selector switch IOI. As shown in the drawings thered amplifier I0! is also connected to the red-green mixer 98, the greenamplifier 96 is connected to the blue-green mixer I04 and the blueamplifier I02 is connected both to the green-blue mixer 91 andjto theredblue mixer I09; The armature II2 of the connector switch IOI isconnected by the conductor 5 I3 to each of the electronic switches I59,I58 and {5? for purposes to appear hereinafter.

The comparator-selector device 92 may comprise any of several devicesbut may conveniently include a cathode tube I2I modified as hereinafterdescribed in detail.

Continuations of the conductor 95, 93 and 94 connect to the combinedrectifiers and amplifiers I3 I, I32 and I33, respectively. The output ofeach of these rectifier and amplifier circuits are connected to, each ofthe, cathode beam control plates I34, i36 andI3I, respectively. Thetarget I38 of the cathode beam I39 is divided into three sections, aninner section I40, a middle section I4I and an outer section I 42. Eachof these sections is of electrically conductive material and isinsulated from the adjacent sections. The conductors I43, I44 and I46con nect each of these sections to amplifier control devices I47, I48and I49, respectively. These amplifier control devices control, eithermechanically or electrically, the magnitude of amplification effected bythe amplifier I 5I for purposes appearing hereinafter. A conductor I52connects the conductor I 43 to each of the conductors I53, I54 and I56which, in turn control, respectively, the electronic switches I51, I58and I59, for purposes appearing hereinafter. Said electronic switchesunder the control of pulses from the conductor I52 select whether theterminals 86, 88 and I4 are energized from the conductors 90, and orfrom the conductors I61, I62 or I63. For purposes of description here itwill be assumed that when conductor I52 is energized the said switcheswill connect conductor II3 to the selector switch I6 and will disconnectthe conductors 80, 85 and 90, and when it is deenergized said switcheswill connect selector switch I6 with conductors 80, 85 and 90 and willdisconnect conductor II3.

Conductors leading from the filter output conductors 59, 6| and 62,respectively, in addition to energizing the conductors 95, 93 and 94 arealso connected to the black printer mixer I64 wherein impulses from eachof said conductors are integrated in predetermined and controllableportions and delivered as a single integrated series of pulses to theconductor I66. Interposed, however, in conductor I66 is the amplifierI5I whereby the pulses delivered by the black printer mixer I64 areamplified by a selected amount. The selection of this amount ofamplification is eifected by the amplifier control devices I41, I48 andI49 according to the energization thereof from the comparator-selectordevice 92 as hereinafter further explained. The conductor I66 thenconnects to the terminal I! of the se lector switch I6.

Operation Although the operation of this device has already beensufficiently indicated above that it is probably now apparent, it willbe further detailed herein for the purpose of completeness.

The two light beams emanating from the sources I and 2, respectively,are gathered by the prism 24 and directed by the lens system 26 onto thescanning mechanism 28. Said scanning mechanism then directs the beam 29onto the transparency 30 for scanning same in any known manner,providing only that such scanning is of sufliciently small elementalareas and is in such a pattern as to produce a smooth end result. Suchscanning methods are well known and, further, one preferred scanningmethod is described in my Patent No. 2,309,048.

The portion of the beam 29 which, as beam 33, strikes the several lightsensitive devices does so as a pulsating beam wherein the pulsationsoriginate in the beam 6. Thus, while the output of the several lightsensitive devices will be a function of the intensity of the total beamstriking each thereof, the output of the respective filter circuits willbe a function only of the portion of the beam 33 which originates in thebeam 6, namely, the portion which is of such a frequency that theresponses thereto in the light sensitive devices will pass therespective electric filter.

These several potentials are then amplified in whatever manner isselected and imposed onto the light valve IT, thereby controlling theintensity of the monochromatic light directed onto the scanning device28 in any predetermined pattern. As the corrected beam strikes thescannin device 28 and is thereby caused to strike the transparency 30,the exposing beam portion thereof, now corrected, will be directed ontothe photo sensitive plate 43. The portion of the corrected beam passingas beam 33 through the lens system 34 and ultimately falling onto thelight sensitive devices 41, 48 and 19 will not afiect the output of thefilter circuits 52 and 53 because each of these beams appears as asteady beam and no part thereof appears at the frequency of the pilotbeam and no beam not of such frequency will have any effect on thepotential appearing in the conductors 59, El and 62.

However, it will be noted that no corresponding provision has thus farbeen described for blocking the portion of the beam 29 which originateswith the pilot beam 6 and passes through the lens system 38 to thenegative 43. This is, of course, of constant intensity and will not beaffected by the corrections made to the exposing beam 1. However, thiswill normally be of little, or no, materiality inasmuch as its magnitudemay be made sufficiently minor with respect to that of the exposing beaml that full and satisfactory correction control may be obtained solelyfrom corrections of said exposing beam. However, in the event that ahigher degree of precision is desired, it is possible to insert withinthe lens system 38 a light valve $8 synchronized by conductor 39 withthe light valve ll so as to block all light having the frequency of saidpilot beam. This would, of course, result in the light emanating fromsaid light valve 68 being of intermittent character but it wouldrepresent solely the product of the exposing beams and hence would besubject to precise intensity control.

Reviewing now the operation of the device in still further detail, themaking and correcting of the green filter (red printing) plate will bestudied.

For this negative it will be assumed. that it is desired to reduce thered portions of the picture, particularly those that are in the blue andgreen areas of portions thereof, to a fractional proportion, as 70%, oftheir normal value in order to compensate for the greater strength ofred reflecting material in the blue-green inks or dyes. Although it iswholly possible to use this equipment to make separation negatives by aprocedure analogous to masking and substantially as described in my saidpatent, I prefer to work directly to a positive representing the reddensities by use of a reversal process, such as used by the subtractivemonopacks.

This enables me to eliminate several steps in th photographic process ofmaking separation negative and then making balanced positive prints ofthe same, which in itself is a time consuming and difficult process andalso enables me to bypass the narrow scale conditions of a paper print.

Therefore to make the red positive plate as preferred, thephotosensitive plate at 43 will be made green-sensitive by the properselectionof photosensitive material and of filters. With the controls83, 19 and 84 set in a manner which has been predetermined asappropriate for the desired correction, and the selector switch '55 setat the terminal 86, the pilot beam scans the transparency and strikeseach of the light sensitive devices. As said pilot beam moves toward agreen element of the transparency, the green sensitive cell 49 isenergized and, through the subsequent circuitry, the light valve [1 inthe exposing beam 1 is caused to increase the intensity of said beam.Thus, the beam 29 is increased and consequently the beam striking thephoto plate 43 is increased in intensity. This has the effect ofincreasing the density in that particular elemental area of the plate.In the subsequent reversal to obtain the positive image, this eiieets areduction of the density in that area, thereby reducing the redstrength.

It is readily seen that any type of negative or positive maskings can besimulated by increasing or decreasing the exposing beam in the properrelations to the intelligence of the interpreting system.

With respect to the blue-green and yellow printer positives, analogousprocedure is adopted, excepting that for the blue-green positive thecircuitry following the red sensitive cell 6? is used and for the yellowpositive the circuitry following the blue sensitive cell 52 is used, andin these cases the armature of the selector switch it is connected tothe terminals 82 or '14 as appropriate. In this way the amplifiers andmixers may be set as desired and, according to the circuitry disclosed,they will modify each other in the proper manner to secure the desiredresults.

A black printing negative in present practice may or may not be used,and in any event it is difficult to prepare. If used, there is theproblem of keeping the blue areas bright and lifelike for if any blackis printed into these areas, the relatively weak blue inks cannotovercome the effect of the black ink and these areas become lifeless anddull. To effect this, there must be met the double problem of modifyingthe color components to produce a true gray result wherever there aretrue black or gray tones in the transparency, and also to eliminate, notmerely reduce, the grays entirely in those portions of the negativecorresponding to those portions of the transparency having a single purecolor, particularly blue. When this is to be done, certain furthercorrections are required in the color separation negatives.

This problem has been met by the gray modulating section 9| modulatingthe tones of gray for so long as the red, blue and yellow colors aresubstantially balanced in the transparency but having thecomparator-selector portion 92 by which other desired results may besecured whenever any of said three colors moves more than apredetermined amount, away from a true balanced condition.

More specifically, the gray modulating circuitry generally indicated SJIoperates in a manner substantially similar to the color modulatingcircuitry III It will, however, normally be set differently than thecolor modulating section fit in order to secure proper rendition of graytones since different correction or" the color separation negatives isoften required for reproducing gray tones as compared to the correctionsrequired for reproducing color tints and tones. This gray modulationsection controls through the conductor H3 and the selector switch "Itthe light valve I'l when the light beam 29 is on a black or gray area inthesame manner as the color modulating section 69 controls said lightvalve when said beam is on an area in which color predominates. In thesecases, it becomes possible to introduce different corrections wheneverthe integrated pilot and exposing beam 29 strikes a portion of thetransparency in which one of the three primary colors predominates overthe other two as compared to the corrections provided for the grayareas. When this occurs, the excitation efiected by one of the electricresponsive devices in the interpreting section 58 will become greaterthan theexcitation of the other cells and corresponding pulses will bedelivered through the conductors 95, 93 and 94 to the oathode controlplates, I34, I36 and I3'I. Thus, the cathode beam I39 will no longerbeequally affected by each of said plates but will move towards one ofthem a distance dependent upon the magnitude of said unbalance.

Therefore, in the preparation of a color separation negative theselector switch It will normally be set at one of the terminals I4, 82and 85 depending upon the color concerned, and the color modulatingsection 60 will normally be preset to effect desired control. So long asa color predominates, the cathode beam I39 will be on either theintermediate or outer target bands MI and M2 and the conductor I52 willnot be energized. Thus, the electronic switches I57, I58 and I59 willpermit the color modulating section fill to act through this selectorswitch I6 to control the light valve I'I. However, when a gray area isreached and the cathode beam I39 strikes the center MI! of the targetarea I43 the conductor I52 will be energized and this in turn willoperate each of the electronic switches I56, I58 and I59 to connect thegray modulating section 9I to the selector switch I6 in place of thecolor modulating section 60 and by it to the light valve I1, and thusprovides a different magnitude of correction, according to the settingof the parts of the gray modulating section 9i, for so long as a grayarea is being encountered by the exposing and pilot beam 29. As soon asbeam 29 returns to a color part of the transparency, the cathode beamI39 will return to the intermediate or outer target rings, the conductorI52 will be de-energized and the electronic switches I51, I58 and I59will also be de-energized, thus again connecting the color modulatingsection 69 to the light valve ll.

When making a black printer negative, the selector switch I6 isconnected to the terminal'fl and the light valve I1 is then controlledthrough the interpreting section 50, the black mixer I64 and theconductor I66. In this case, neither the color modulating section 60 northe gray modulating section 9! has any function but thecomparator-selector section .92 continues to be important. Here, theposition of the cathode beam I39, in pursuance of whether the exposingbeam I39 is on a gray or a color area of the transparency, willdetermine through selection of the amplification selectors I41, I48 andI49 the magnitude of amplification effected in the amplifier I5 I. Thus,in the purely gray sections there will be a given value of the densityappearing in the black printer, or a normal exposure value. In theslightly colored parts of the transparency, but those still having somegray present, there will be a slightly greater value of density effectedin the black printer negative by a diiferent magnitude of control in thelight valve Il being super-imposed upon the impulses from theintegrating section 50, and in the pure color sections there will be astill further amplification effected by the amplifier I5I by which tocause a complete over-exposure or greater density in these portions ofthe black printer negative regardless of the impulses supplied to theblack printer mixer from the interpreting section 59.

Thus, the black printer negative when reversed by subsequent developmentwill produce a black printer positive image with well exposed detail insections where the colors are balanced, that is, the gray or blackareas. In the areas which contain only solid or deep colorcharacteristics, that is, some color and some gray, there will be lessdensity and, finally, in the areas where the colors are pure mixtures ofcolor and no grays are present the printer will be completely lacking inany density at all. Thus, an ideal black printer will be provided.

It will be evident that, while I have used two target bands outside ofthe center area I40, to illustrate my invention, any number of suchbands with corresponding gradations in control or" the amplifier I5I maybe employed where desired for more precise control.

Modification shown in Figure 2 The modification shown in Figure 2 mayalso be utilized for copying moving picture films with proper colorcorrection. The structure and operation of the device is the same asthat described above excepting only that here there are provided twoadditional light sources 200 and 2M with corresponding additional lightvalves 2&2 and 2&3. In this embodiment, each of the light sources isprovided with a filter, as indicated at 204, 206 and 201, to render saidbeams monochromatic prior to striking the mixing prism 2d. Thus, therespective light valves will each control one color of the integratedexposing beam 21. The light valves are here connected into the colormodulating system (ill by conductors corresponding to the terminals 86,82 and M in the structure shown in Figure 1. That is, the light source2M and the light valve 2M, being asso ciated with a green filter arearranged with the conductor 96! in Figure 1. The light source 2% and thelight valve 202, being associated with a blue filter, are arranged withthe conductor 85 of Figure 1. The light source I and the light valve I Ibeing here associated with a red filter 291 are arranged withtheconductor 3%, associated in Figure l with the terminal is. Thetransparency and negative holders associated in Figure 1 with thetransparency 39 and the negative 43 are here modified to receive thefilm 230 to be copied and the film 243 to be exposed, respectively. Therest of the structure and circuit is the same as that shown in thatportion of Figure 1 comprising generally the interpreting section 50 andthe color modulating section 60, as will be obvious from the inspectionof the drawings. The operation is also identical. Accordingly, noadditional detailed description is necessary here, excepting to say thatin this instance the source of monochromatic exposing beams operatesimultaneously but in the same manner and with the same results as withthe single beam 1 shown in Figure l.

Modification of Figure 3 Figure 3 shows a device wherein the single beam29 may, if desired, be split into several parts for the purpose ofsimultaneously exposing more than one transparency. The beam 29 passingthrough the lens held within the lens holder 38 passes first through thetransparent mirror 38! which directs a portion of the light from saidbeam to the transparency 382, and the portion passing through saidmirror 301 falls upon a similar mirror 303. A portion of the light isdeflected to the transparency 304, and the balance passes on throughsaid last named mirror to expose the transparency 43 in the manner aboveset forth. This forms no part of my invention as such and is mentionedmerely to indicate the versatility of application of the subject matterof the invention.

I claim:

1. In an electrical optical system for reproducing a color photograph,the combination: means producing a pilot beam of poly-chromatic light,the intensity of said beam being non-constant with its intensity peaksoccurring at a predetermined frequency; means providing a beam ofmonochromatic light of constant intensity constituting an exposing beam;an optical system gathering said beams into a single beam and directingsame onto a single elemental area of a transparency and means causingsaid single beam to scan a plurality of elemental areas of saidtransparency; a light sensitive electric device; means holding lightsensitive material; means directing a portion of the light passingthrough said transparency onto said light sensitive electric device anddirecting another portion of said light onto said light sensitivematerial; a frequency responsive filter circuit operatively associatedwith said light sensitive electric device and adapted to transmit onlyoutput impulses therefrom of said frequency; a light valve in the pathof said monochromatic beam and means including controllable andselectable means comprising a modulating section connecting the outputof said filter circuit to said light valve.

2. In a device for exposing light sensitive materials from a coloredoriginal and effecting predetermined modifications from the colorcharacteristics of said original, the combination comprising: a sourceof monochromatic light of constant intensity for originating an exposingbeam; a source of intermittent poly-chromatic light for originating apilot beam, the frequency thereof being of a predetermined value; meanscausing a beam of light comprising constituents from both of saidsources to scan said colored original by elemental areas; a lightsensitive electrical device; an optical system receiving a portion ofthe light emanating from said colored original as a result of said pilotbeam falling thereon and directing same onto said light sensitiveelectrical device; a further optical system receiving another portion ofthe light emanating from said colored original as a result of saidscanning beam falling thereon and directing same onto said lightsensitive material; an electrically controllable light value in the pathof said exposing beam; an electrical filter circuit receiving the outputof said light sensitive electrical device, said circuit constructed topass only impulses of a frequency equal to said pre-determined value;conductor means connecting said filter circuit with said light valve.

3. The apparatus claimed in claim 2 including a light valve in saidfurther optical system and means operating same in such synchronism withthe frequency of said pilot beam that said valve blocks passage of lightwhen said pivot beam is on and permits passage of light when said pilotbeam of constant intensity is off.

4. In a device for exposing light sensitive material from a coloredoriginal and effecting predetermined modifications from the colorcharacteristics thereof, the combination comprising: means providing abeam of substantially monochromatic light and constituting an exposingbeam; means providing an intermittent beam of poly-chromatic lightincluding each of the three primary colors and constituting a pilotbeam, the intermittenoy thereof being of a predetermined frequency;means causing a beam of light comprising constituents from both of saidsources to scan said colored original by elemental areas; threeelectrical light sensitive devices, each sensitive to one andsubstantially only one of the primary colors; an optical systemreceiving a portion of the light emanating from said colored original asa result of said scanning beam falling thereon and directing same ontoeach of said light sensitive devices; a further optical system receivinganother portion of the light emanating from said colored original as aresult of said scanning beam falling thereon and directing same ontosaid light sensitive material; an electrically controllable light valvein the path of said exposing beam; three electrical filter circuitsreceiving respectively the output of each of said light sensitivedevices, each of said filter circuits being constructed to pass onlyimpulses of said predetermined frequency; an electrically controllablelight valve in the path of said exposing beam; a modulating circuitconnecting one, selectively, of said filter circuits to said last namedlight valve.

5. In a device for exposing light sensitive material from a coloredoriginal and effecting predetermined modifications from the colorcharacteristics thereof, the combination comprising: means providing abeam of substantially constant intensity of substantially monochromaticlight and constituting an exposing beam; means providing a beam ofpolychromatic light including each of the primary colors andconstituting a pilot beam, and means in the path thereof rendering saidbeam intermittent at a predetermined frequency; means causing a beam oflight comprising constituents from both of said sources to scan saidcolored original by elemental areas; three electrical light sensitivedevices, each sensitive to one and substantially only one of the primarycolors; an optical system receiving a portion of the light emanatingfrom said colored original as a result of said pilot beam fallingthereon and directing same onto each of said light sensitive devices;chromatic selection means; a further optical system receiving anotherportion of the light emanating from said colored original as a result ofsaid scanning beam falling thereon and directing same onto saidchromatic selection means; a plurality of optical means directingsubstantially monochromatic light emanating from said selection means tosaid light sensitive material; an electrically controllable light valvein the path of said exposing beam; three electrical filter circuitsreceiving respectively the output of each of said light sensitivedevices, each of said filter circuits being constructed to pass onlyimpulses of said predetermined frequency; an electrically controllablelight valve inthe path of said exposing beam; a modulating circuitconnecting one, selectively, of said filter circuits to said last namedlight valve.

6. In a device for exposing light sensitive materials from a coloredoriginal and efiecting predetermined modifications of the colorcharacteristics thereof, the combination comprising: means providingthree independent beams of substantially monochromatic light andrepresenting the three primary colors, each of said beams being ofconstant intensity and constituting an exposing beam; means providing anintermittent beam of poly-chromatic light including each of the threeprimary colors and constituting a pilot beam, the intermittency thereofbeing of a predetermined frequency; means causing a beam of lightcomprising constituents from both of said sources to scan said coloredoriginal by elemental areas; three electrical light sensitive devices,each sensitive to one and substantially only one of the primary colors;an optical system receiving a portion of the light emanating from saidcolored original as a result of said scanning beam falling thereon anddirecting same onto each of said light sensitive devices; a furtheroptical system receiving another portion of the light emanating fromsaid colored original as a result of said scanning beam falling thereonand directing same onto said light sensitive material; an electricallycontrollable light valve in the path or each of said exposing beams; amodulating circuit connecting one, selectively, of said filter circuitsto each, respectively, of said last named light valves.

'7. A device described in claim 4, including also an electronic switchinterposed between said color modulating section and said light valve;2. second color modulating section connected in parallel with said firstmentioned color modulating section between said filter circuit and saidelectronic switch whereby one color modulating section or the otherthereof will control said light valve depending upon the position ofsaid electronic switch; means responsive to said pilot beam after samehas passed through the transparency for placing said electronic switchin one position when said portion of said pilot beam is substantiallypoly-chromatic and placing said electronic switch in another positionwhen said portion oi said pilot beam is substantially monochromatic.

8. A device described in claim 4 including also an electronic switchinterposed between said color modulating section and said light valve; asecond color modulating section connected in parallel with said firstmentioned color modulating section between said filter circuit and saidelectronic switch whereby one color modulating section or the otherthereof will control said light valve depending upon the position ofsaid electronic switch; means connected tothe output of said filtercircuit and connected to said electronic switch for holding said switchin one position when the output of each of, said circuitsare ofsubstantially the same magnitude and for changing the position of saidswitch when one of said outputs exceeds in magnitude the output ofanother of said filter circuits by a predetermined amount.

9. The circuit described in claim 2 including also: a variable amplifierinterposed in said conductor means; comparator means connected to theoutput of each of said filter circuits and controlling the magnitude ofamplification of said amplifying means such that said amplifying meanseiiects one ratio of, amplification when said filter circuits are ofsubstantially equal output and effects another ratio of amplificationwhen the output of said filter circuits become unbalanced.

10. In an electrical optical system for reproducing a color photograph,the combination: means producing apilot beam of polychromatic light, theintensity of said beam being non-constant with its intensity peaksoccurring at a predetermined frequency; means providing a beam ofmonochromatic light of constant intensity constituting an exposing beam;an optical system, gathering said beams into a single beam and directingsame onto a single elemental area of a transparency and means causingsaid single beam, to scan a plurality of elemental areas of saidtransparency; a light sensitive electric device; means holding lightsensitive material; means directing a portion of the light passingthrough said transparency onto said light sensitive electric device anddirecting another portion of said light onto said light sensitivematerial; a frequency responsive filter circuit operatively associatedwith said light sensitive electric device and adapted to transmit onlyoutput impulses therefrom of said frequency; a light valve in the pathof said monochromatic beam and means connecting the output of saidfilter circuit to said light valve.

11. A device for exposing light sensitive material from a coloredoriginal and effecting predetermined modifications from the coloredcharacteristics thereof comprising the combination: means providing abeam of substantially monochromatic light and constituting an exposingbeam; means providing an intermittent beam of polychromatic light andconstituting a pilot beam, the intermittency thereof being of apredetermined frequency; means causing a beam of light comprisingconstituents from both of said sources to scan said colored original byelemental areas; a plurality of electrical light sensitive devices, saidplurality being equal to the number of colors within said polychromaticbeam, each sensitive to one and substantially only one of said colors;an optical system receiving one portion of the light emanating from saidcolored original as a result of said scanning beam falling thereon anddirecting same onto each of said light sensitive devices; a furtheroptical system receiving another portion of the light emanating fromsaid colored original as a result of said scanning beam falling thereonand directing same onto said light sensitive material; an electricallycontrollable light valve in the path of the exposing beam; a pluralityof electrical filter circuits; said plurality being equal in number tothe number of colors above mentioned; receiving respectively the outputof each of said light sen- 15 sitive devices, each of said filtercircuits being constructed to pass only impulses of said predeterminedfrequency; an electrically controllable light valve in the path of saidexposing beam; a modulating circuit connecting each of said filtercircuits selectively to said light valve.

12. A device described in claim 4 including also an electronic switchinterposed between said color modulating section and said light valve; asecond color modulating section connected in parallel with said firstmentioned color modulating section between said filter circuit and saidelectronic switch whereby one color modulating section or the otherthereof will control said light valve depending upon the position ofsaid electronic switch; a target comprising a plurality of concentricelectric conductors insulated from each other, the center one thereofbeing connected to hold said electronic switch in one position when sameis energized and said electronic switch automatically assuming anotherposition when said center conductor is deenergized, means directing afiow of electrons onto said target, and a plurality of control platesarranged about the normal path of said beam to cause same to strike saidcenter conductor when, and only when, same are substantially .uniformlycharged, means imposing a charge onto each of said plates proportionalto the intensity of the output of each filter circuit.

13. A device described in claim 4 including also an electronic switchinterposed between said color modulating section and said light valve; asecond color modulating section connected in parallel with said firstmentioned color modulating section between said filter circuit and saidelectronic switch whereby one color modulating section or the otherthereof will control said light valve depending upon the position ofsaid electronic switch; a target comprising a plurality of adjacentelectric conductors insulated from each other, one thereof beingconnected to hold said electronic switch in one position when same isenergized and said electronic switch automatically assuming anotherposition when said center conductor is deenergized, means directing aflow of electrons onto said target, and a plurality of control platesarranged about the normal path of said beam to cause same to strike saidone conductor when, and only when, same are substantially uniformlycharged, means connecting the output of each filter circuit with one ofsaid control plates for imposing a charge onto each of said platesproportional to the intensity of the output of each filter circuit.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,309,048 Curry Jan. 19, 1943 2,565,399 Simmon Aug. 21, 1951

